In recent years our society and the world in general has become increasingly more and more energy dependent. The resulting rise in energy demands have coupled with rising costs for petroleum based fuels to kindle an increased interest in alternative fuels that once may have been considered too costly to produce. Of particular interest are fuel sources that are considered to be ‘renewable.’ One of these renewable and alternative energy sources is commonly referred to as biomass.
Biomass generally includes living and recently dead biological material which can be used as fuel or for industrial production. Most commonly, biomass refers to plant matter grown for use as biofuel, but it also includes plant or animal matter used for production of fibers, chemicals or heat. Biomass may also include biodegradable wastes that can be burned as fuel, but it excludes organic material which has been transformed by geological processes into substances known as fossil fuels such as coal or petroleum.
Typical sources of biomass include several plants such as miscanthus, switchgrass, hemp, corn, poplar, willow and sugarcane. The particular plant used is usually not very important to the end products, but it does affect the processing of the raw material. Production of biomass is a growing industry as interest in sustainable fuel sources is growing. While the term biomass is also useful to identify plants where some of the plant's internal structures may not always be considered living tissue, such as the wood of a tree, and even though this biomass was produced from plants that convert sunlight into plant material through photosynthesis, the use of the term ‘biomass’ herein is by definition limited to agricultural plant growth that is harvested on a regular and periodic basis as part of an agricultural enterprise.
A major source of this biomass results from agricultural activities wherein the plant growth is produced specifically as a biomass product or alternatively is the residue of grain based agricultural crops. Traditionally, agricultural crop residues have been left on the field and reworked into the field's topsoil layer with the intent to return those nutrients removed during the crop's growth cycle and stored in the residue. Studies have revealed that sufficient and even optimal tilth levels in the topsoil layer can be maintained by returning only a fraction of the agricultural crop residue from a particular growth cycle. Until recently, there has been no particular incentive to remove the excess residue from agricultural fields other than for other agricultural uses such as bedding materials or low grade feed for agricultural livestock. However, with the interest in biomass as a renewable energy source, biomass can also now be considered an additional income source from the agricultural growth cycle to supplement the income derived from the harvested grains.
The desire to also harvest biomass from agricultural fields is tempered by the necessary caution to refrain from removing an excess of biomass and thus gradually depleting the topsoil nutrient levels after successive years of harvests. The nutrient needs of the topsoil vary geographically and even vary within the boundaries of a particular field such that determining harvestable quantities is location specific problem and not governed by general parameters applicable across an entire field. Such determinations must be made by an intelligent system that analyzes the topsoil layer concurrent with the harvesting of the biomass.
The composition of biomass is controlled by genetics, and consequently the production and subsequent harvesting of specific genetic lines can result in a product which allows biomass utilization processes to be optimized. For example, if one is using cellulose from corn fodder biomass to produce ethanol via a fermentation process, the value of a unit of biomass increases as the percentage of cellulose increases. Similarly, a company producing an adhesive through a chemical process will find value in corn genetic lines with high lignin levels. In all cases, moisture is invariably a critical factor since excess moisture reduced dry weight in a unit of biomass and increases transportation costs; can also lead to spoilage within a biomass unit. Moisture typically has to be removed during the pre-processing steps to enable particle size reduction, etc.
The concept that the chemical composition of plant biomass is influenced by a wide range of uncontrolled factors which vary across a field such as soil type, effective moisture availability, soil microflora (type & levels), etc. is not widely understood. Also less widely understood is that the chemical composition of plants can also be influenced by production management practices, such as fertilization, use of plant hormones (both natural and synthetic), irrigation, etc.
The resulting variation in biomass quality attributes creates the need for defining the physical source of a unit of biomass and the need for acquiring and tracking quality attributes at biomass harvesting/packaging (as well as during subsequent steps). Common attributes to be tracked may include unit weight, moisture percentage, lignin percentage, cellulose percentage, hemicellulose percentage, and other attributes.
The value of maintaining traceability of discrete biomass units is enhanced when the biomass source has discrete attributes (with positive and negative value depending upon the specific biomass utilization process) resulting from plant genetics, soil characteristics, production practices, etc. The value of maintaining traceability of discrete biomass units is further enhanced when the harvesting or packaging system has components which objectively characterize the unique attributes of a specific unit of biomass such as physical, chemical, biological, etc. components.
To optimize the value of the biomass being harvested and offered for sale, the producer needs to know the source location and the critical quality attributes relate to physical, chemical and biological properties of each biomass unit relative to the anticipated end use. Therefore, the optimization of the value of the biomass being purchased and subsequently utilized in a specific biomass utilization process depends upon knowledge of the source location and critical quality attributes related to physical, chemical and biological properties of each biomass unit. The biomass industry has implemented a variety of schemes for tracking discrete units of biomass. These tracking schemes have typically been borrowed from the larger logistics world. Tracking system examples include physical labels, barcodes in both 1D, 2D and 3D constructs, RFID systems, etc. These systems add complexity and expense to the logistics process associated with the harvesting, transport and storage of biomass.
Once the biomass units have been produced and collected they are often accumulated and arranged into stacks while awaiting use in various industrial processes (co-firing, gasification, fast pyrolysis, chemical extraction, fermentation, etc.) optimized for the processing of biomass. All of these processes have definable limits on the moisture content of the feedstock. Some of these limits are defined by the requirements for using a dry grind process for particle size reduction prior to other process steps while others are limited by process requirements per se such as moisture limits in fast pyrolysis. Regardless, there is typically a common need to store and protect the biomass-based raw materials from the weather and natural degradation processes.
The biomass is frequently stored in stacks of bales of various sizes which are then manually covered by tarps of various kinds. The parking process is labor intensive and exposes workers to a number of significant occupational hazards including falls. Covering a stack of biomass while meeting the worker protection requirements established by OSHA is difficult. Risk to the workers is particularly acute when the workers are required to use ladders for access to the top of the stack or to secure the tarp or the film to the side of the stack. The stacks are frequently built six to eight bales in height (nominally 16 to 32 feet) or more. These heights are far beyond OSHA limits for unprotected worker activities.
Because of the nature of the biomass and the fact that the bales themselves comprise the supporting structure of the stack, individuals working on the top of the stack are unprotected by either railings or other restraint systems and thus are subject to falls from edges of the stack. In addition, the stacking process can create voids and crevices between bales into which a worker can accidentally step, especially when the void or crevice may be covered by a thin layer of biomass residue.
Therefore, a reliable and low cost system for covering a stack of bales to protect the bales from the elements without exposing workers to prohibited activities in the workplace is needed.